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Physiology and Biochemistry

Differential Effect of Light on Spore Germination of Exserohilum turcicum on Corn Leaves and Corn Leaf Impressions. Yehouda Levy, Lecturer, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52 100, Israel; Yigal Cohen, professor, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52 100, Israel. Phytopathology 73:249-252. Accepted for publication 3 June 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-249.

The effect of light on spore germination of Exserohilum turcicum was investigated in vitro on collodion corn leaf impressions and in vivo on leaf surfaces of susceptible corn plants. On collodion impressions, the percentage spore germination under light at a photon flux density of 150 μEm-2sec-1 was the same as in darkness. On host leaf surfaces, light at a photon flux density of 150 μEm-2sec-1 inhibited spore germination by 85% (at 20 C) compared to the dark control. Blue light was more inhibitory than red light to spore germination in vivo. Inhibition under light persisted in the presence of dichlorophenyldimethylurea, a photosynthesis inhibitor. As a result of the inhibition of spore germination, no infection occurred on leaves irradiated during the wet infection period. It is suggested that light inhibited spore germination on the leaf surface indirectly by some physiological change in the host.

Additional keywords: Helminthosporium turcicum, northern corn leaf blight.